ANALYSIS & OPINION

Know your AM design process

Following speaking at the Mach exhibition in Birmingham at the beginning of April, Louise Geekie, project manager at Croft Additive Manufacturing, gives her views on how additive manufacturing can be optimised through the design process

Understanding customers’ needs can drive design in additive manufacturing. Understanding the entire design process means additive manufacturing (AM) design freedoms can be exploited to create new products that offer solutions to particular problems.

One example of this is designing woven wire mesh filters for a pharmaceutical company. The company wanted a filter that could be cleaned more effectively, so Croft created an AM woven wire mesh equivalent to remove the recesses between the wires where contamination occurred.

Croft Additive Manufacturing, the sister company to Croft Filters, has been using metal selective laser melting (SLM) to create new and potentially high-value filtration products.

The SLM AM process involves a layer of metal powder being applied to a base plate, which is then fused by a laser according to the CAD design. This process is repeated to create the finished product.

Unlike some plastic 3D printers which can fabricate components without supports, SLM AM requires the component to be fixed to a build plate. In addition, where components have overhanging parts of less than 45°, build supports are also required. For example, the sides of Croft’s AM-produced ‘holes in-line’ filter are self-supporting during the build, but the top of the filter requires build supports from the base plate. By maximising the amount of self-supporting areas within a component and minimising the amount of build supports, more successful AM builds can be created.

Metal AM can also deliver improved filter products in a shorter time period. Whereas conventional wedge wire filters are formed from multi-parts with a long lead time, a fully self-supporting AM wedge wire filter can be designed and produced as a single part with shortened lead time.

A common traditional method for constructing filters is by using a perforated plate and a woven wire mesh. While the perforated plate gives the filter overall strength, the aperture size of the woven wire mesh determines the size of the filter.

Creating filters in this traditional way can mean that when fluid is pumped through it, turbulence is created, which results in resistance across the filter, called the pressure drop. To overcome this resistance, more pumping energy is required, increasing the end-user’s energy costs. In a bid to overcome this, Mark Burns, director at Croft Additive Manufacturing, had the idea that by putting holes in a filter in-line with the fluid flow, the amount of resistance produced would be reduced, along with the pumping energy requirements.

The design couldn’t be made with conventional methods, but it could with additive manufacturing, and, after visiting FabLab in Manchester to see 3D printing in action, the team at Croft quickly got to work designing the ‘holes in-line’ filter. Firstly, the holes were aligned to the direction of flow, to potentially decrease the resistance; then the support was made by adding a structure around the holes, creating the filter as a single part.

A plastic (ABS) prototype was built at FabLab and, when tested, the resistance over a range of flow rates was lower compared to a comparable conventional filter, decreasing the pumping energy and reducing cost, as Mark Burns had predicted.

Croft is now using its experience with the design process for additive manufacturing to develop non-filtration products for various customers, in prototyping and component manufacture, to increase the industrial adoption of metal 3D printing.

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Croft Additive Manufacturing (CAM) is a Warrington UK-based business founded by brothers Mark and Neil Burns and fellow entrepreneur, Darren Travis. The specialist company provides metal additive manufacturing opportunities to a range of industries in the UK and overseas. Using a Realizer SLM-250 metal 3D printing machine, CAM’s in-house team offers innovative, flexible product design and manufacturing services.

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Analysis and opinion